Handoff analysis of the hierarchical cellular system

As mobile telephone traffic demands increase in the future, interest in cellular systems with a hierarchical structure will grow. Hierarchical cellular system can provide high system capacity, efficient channel utilization, and an inherent load-balancing capability. In this type of system, calls blocked in a microcell flow over to a macrocell which is superimposed on a number of microcells. When overflow calls which are accomodated in a macrocell cannot be returned to a microcell, the macrocell channels become saturated. Thus, we propose a hierarchical cellular system with an underflow scheme which permits overflow calls to return to microcells. We model this underflow scheme and analyze system performance.